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/* @(#)s_frexp.c 5.1 93/09/24 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunPro, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

 * ====================================================

 */

/*

FUNCTION

       <<frexp>>, <<frexpf>>---split floating-point number

INDEX

        frexp

INDEX

        frexpf

ANSI_SYNOPSIS

        #include <math.h>

        double frexp(double <[val]>, int *<[exp]>);

        float frexpf(float <[val]>, int *<[exp]>);

TRAD_SYNOPSIS

        #include <math.h>

        double frexp(<[val]>, <[exp]>)

        double <[val]>;

        int *<[exp]>;

        float frexpf(<[val]>, <[exp]>)

        float <[val]>;

        int *<[exp]>;

DESCRIPTION

        All non zero, normal numbers can be described as <[m]> * 2**<[p]>.

        <<frexp>> represents the double <[val]> as a mantissa <[m]>

        and a power of two <[p]>. The resulting mantissa will always

        be greater than or equal to <<0.5>>, and less than <<1.0>> (as

        long as <[val]> is nonzero). The power of two will be stored

        in <<*>><[exp]>.

@ifinfo

<[m]> and <[p]> are calculated so that

<[val]> is <[m]> times <<2>> to the power <[p]>.

@end ifinfo

@tex

<[m]> and <[p]> are calculated so that

$ val = m \times 2^p $.

@end tex

<<frexpf>> is identical, other than taking and returning

floats rather than doubles.

RETURNS

<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,

or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.

PORTABILITY

<<frexp>> is ANSI.

<<frexpf>> is an extension.

*/

/*

 * for non-zero x

 *      x = frexp(arg,&exp);

 * return a double fp quantity x such that 0.5 <= |x| <1.0

 * and the corresponding binary exponent "exp". That is

 *      arg = x*2^exp.

 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg

 * with *exp=0.

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

static const double

#else

static double

#endif

two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */

#ifdef __STDC__

        double frexp(double x, int *eptr)

#else

        double frexp(x, eptr)

        double x; int *eptr;

#endif

{

        __int32_t hx, ix, lx;

        EXTRACT_WORDS(hx,lx,x);

        ix = 0x7fffffff&hx;

        *eptr = 0;

        if(ix>=0x7ff00000||((ix|lx)==0)) return x;       /* 0,inf,nan */

        if (ix<0x00100000) {            /* subnormal */

            x *= two54;

            GET_HIGH_WORD(hx,x);

            ix = hx&0x7fffffff;

            *eptr = -54;

        }

        *eptr += (ix>>20)-1022;

        hx = (hx&0x800fffff)|0x3fe00000;

        SET_HIGH_WORD(x,hx);

        return x;

}

#endif /* _DOUBLE_IS_32BITS */